Grain Size Distribution of a Modern Tidal River: A Case Study of Calabar River, South-South Nigeria

The influence of sedimentary processes and environmental factors on the distribution of grain size facies in a modern day river with daily tidal influence was investigated using statistical parameter from grain size analysis of sediments derived from 45 sampled locations over a 15km segment and bathymetric readings from nine (9) transect of the Calabar tidal river, Southern Nigeria. The bathymetry of the river was deduced from depth sounding and were transformed into contour values. The distribution of the four grain size parameters, mean (Mz), sorting (OT), skewness (SKI) and kurtosis (KG), were sensitive to current energy changes which influences the dynamics of erosion, transportation, and depositional velocity controlled in the Calabar River by daily ebb and flood tidal regime and the gravitational downstream flow direction of the river. The mean grain size was observed to be coarser upstream and within the meander, fining gradually towards the river mouth downstream. Sorting, improved downstream, from extremely poorly sorted, at the meander to moderately sorted at the river mouth. The skewness indicated negative skeweness downstream while positively skewed upstream. While the kurtosis was generally leptokrtic downstream and very leptokurtic upstream. Based on the mean grain size parameter the sediments were differentiated into coarse, fine, and mud grained facies.